Commercial preparation of fruit preparatory to canning or using it in baked goods has always been an urgent matter, in view of the tendency of the fruit to discolor and spoil rapidly. Ordinary refrigeration has not been considered as sufficient to halt or significantly retard this tendency, and even freezing has required considerable preparatory processing in order to preserve the taste and appearance of the fruit.
It has been common practice to soak fruit, particularly pieces of apples, in a solution containing sodium bisulfite and citric acid prior to freezing, in order to prolong the storage life of the frozen pieces. Wide variations in the concentration of the bisulfite and the citric acid have been tried, but no process has been found which has been considered capable of doing anything more than extending the storage life of the frozen product. It has not been recognized that possible ranges of these chemicals exist which would eliminate the need for freezing, and also substantially further prolong the storage life of the frozen product.